Abstract:

The invention relates to a device for turning over sheet material,
preferably sheets of printing material, in a printing machine, preferably
for verso-printing, preferably in a digital printing machine, preferably
an electrophotographic printing machine, said device comprising driven
web-shaped segments extending essentially parallel to each other over at
least one section, said web-shaped segments clamping the indi-vidual
sheet between them and thus transporting said sheet along a transport
path, thus turning over said sheet. The object of the invention is to
provide a turn-over device of the aforementioned type, which grasps the
sheets with the belt segments and guides them in a manner so as to be
turned over, in an easier and more secure manner. This object is achieved
in that the clamping belt segments move together on the sheet transport
path around at least one deflecting element which deflects them by
approximately 180° in such a manner that the previously upper side
of the sheet becomes the lower side of the sheet

Claims:

1. Device for turning over sheet material, preferably sheets of printing
material, in a printing machine, preferably for verso-printing,
preferably in a digital printing machine, preferably an
electrophotographic printing machine, said device comprising driven
web-shaped segments extending essentially parallel to each other over at
least one section, said web-shaped segments clamping the individual sheet
between them and thus transporting said sheet along a transport path,
thus turning over said sheet,characterized in thatthe clamping belt
segments move together on the transport path around at least one
deflecting element which deflects them by approximately 180.degree. in
such a manner that the previously upper side of the sheet becomes the
lower side of the sheet.

2. Device as in claim 1, characterized in that at least two deflecting
rollers are arranged successively on the sheet transport path, said
rollers ultimately also returning the individual sheet into its original
transport direction.

3. Device as in claim 2, characterized in that at least two deflecting
elements are oriented at an angle of approximately 45.degree. relative to
the advance direction of the belt segments.

4. Device as in claim 3, characterized in that the minimum of two
deflecting elements are essentially oriented parallel or at right angles
relative to each other.

5. Device as in one of the claims 2 through 4, characterized in that the
minimum of two deflecting elements is supplemented by at least a third
deflecting element that extends essentially in transverse direction to
the advance direction of the belt segments.

6. Device as in one of the claims 2 through 5, characterized in that the
course of the belt segments is substantially looped to have approximately
the shape of a T, in which case the individual sheet is
transported--essentially approximately in transverse direction--out of
its original transport direction in order to be later again transported
into its original transport direction.

7. Device as in one of the previous claims, in particular as in claim 6,
characterized in that the path, along which the individual sheet is
carried, provides turning by a total of approximately 540.degree.,
whereby the sheet's upper side becomes its underside, again its upper
side and finally again its underside.

8. Device as in one of the previous claims, characterized in that, in
order to form all the belt segments, only one single, appropriately
looped, belt is required.

9. Device as in one of the previous claims, characterized in that at least
one pair of deflecting elements is provided, with which the deflecting
elements cooperate--counter-rotating--as counter-bearing elements and
form between them a guide nip for the clamping belt segments.

10. Device as in claims 8 and 9, characterized in that at least one first
pair of cooperating deflecting elements for moving freely returning belt
segments toward each other is provided to form the clamping belt
segments, and a second pair of cooperating deflecting elements for the
separation of the clamping belt segments is provided to form the freely
returning belt segments.

11. Device as in claim 10, characterized in that the region of the first
pair of cooperating deflecting elements can be provided for feeding the
sheet to be turned over, and the region of the second pair of cooperating
deflecting elements can be provided for ejecting the turned over sheet.

12. Device as in one of the previous claims, in particular as in claim 10
or 11, characterized in that the deflecting elements are arranged and/or
dimensioned in such a manner that the clamping belt segments are located
in the space between freely returning belt segments, in particular the
freely returning belt segments.

Description:

[0001]The invention relates to a device for turning over sheet material,
preferably sheets of printing material, in a printing machine, preferably
for verso-printing, preferably in a digital printing machine, preferably
an electrophotographic printing machine, said device comprising driven
web-shaped segments extending essentially parallel to each other over at
least one section, said web-shaped segments clamping the individual sheet
between them and thus transporting said sheet along a transport path,
thus turning over said sheet.

[0002]A device for turning over sheets of the aforementioned type is
known, for example, from DE 100 59913 C2.

[0003]The known device which actually functions quite well can pose
problems in certain situations. Printing material sheets having certain
dimensions, weights per unit area, stiffnesses or a curl can be turned
over only with difficulty or not at all. Also, with some printing
materials, the fiber advance direction affects the turning behavior of
the sheets. In particular, sheets having a low weight per unit area
and/or low stiffness collapse easily within themselves during the
turn-over process when certain dimensions are exceeded. Light-weight
materials also tend to crease. Sheets exhibiting great stiffness and/or a
high weight per unit area need to be additionally guided during the
turn-over process, which can be achieved, for example, with guides
consisting of sheet metal, wires or the like. However, as a result of
this, the sheets may be damaged. Sheet jams may be caused by each of the
above circumstances. Curls and/or oil smears, in particular caused by
toning oil, can exacerbate the problems.

[0004]The service life of the web-shaped belts of the known turn-over
devices is relatively limited. In addition, older belts reduce the
transport quality of the belts. Likewise, the production of the belts is
relatively complex. With the known device, the sheets are held centered
by the belts and are turned in a screw-like manner by helically turned
belts. As a result of this, the belts are stressed relatively heavily,
the balance of the sheets is relatively instable, the sheets' lateral
overhang is large thus offering air resistance during the turn-over
process, and a crossing and clamping of the belt segments required for
turning over and holding the sheets must be maintained by guide rollers
with collars.

[0005]The object of the invention is to provide a turn-over device of the
aforementioned type, which grasps the sheets with the belt segments and
guides them in a manner so as to be turned over in an easier and more
secure manner.

[0006]In accordance with the invention, this object is achieved in that
the clamping belt segments move together on the sheet transport path
around at least one deflecting element which deflects them by
approximately 180° in such a manner that the previously upper side
of the sheet becomes the lower side of the sheet.

[0007]In the inventive turn-over device, the individual sheet material
together with the belt segments clamping them is deflected and turned
over advantageously, not in a helical direction, but essentially in a
looping direction. This provides some advantages. For example, as a
result of the joint deflection, the clamping effect of the belt segments
is enhanced and maintained in a more reliable manner. Thus, the sheet
material can be guided in a more stable manner and the turn-over process
is particularly controlled and determinated. In addition, the web-shaped
segments can also be configured wide, almost to any width, in particular
configured more belt-like. This results in an improved guide surface,
even for larger and stiffer sheets, and in less stress on the belt
segments. The latter also increases the service life of the belt
segments. It is also possible to use several parallel moving belt
segments. As the contact surface of the sheets becomes larger, the
material properties of the belt segments become less critical, so that
said segments can be manufactured in a simpler and less expensive manner.

[0008]When the sheets are turned over--as is also true of the known
turn-over device--the leading end of the sheet before said sheet is
turned over remains the leading end after said sheet has been turned
over. This is favorable in particular regarding the registration of such
a sheet in a printing machine.

[0009]A modification of the inventive device provides that at least two
deflecting rollers are arranged successively on the sheet transport path,
said rollers ultimately also returning the individual sheet into its
original transport direction. For the inventive guiding of the sheet, it
is not so essential how often the sheet--with the belt segments--is
guided around the deflecting elements. Even various directional changes
are always possible, so that the turn-over path can be adapted
particularly well to miscellaneous situations, in particular in a
printing machine.

[0010]Therefore, another modification of the invention provides that at
least two deflecting elements are oriented at an angle of approximately
45° relative to the advance direction of the belt segments, and/or
that the minimum of two deflecting elements are essentially oriented
parallel or at right angles relative to each other.

[0011]Also, it is possible that the minimum of two deflecting elements be
supplemented by at least a third deflecting element that extends
essentially in transverse direction to the advance direction of the belt
segments, whereby the advance direction of the belt segments need not
correspond--at least along sections--to the ultimately desired transport
direction of the sheets. However, changes of the transport direction are
also inherently possible with the inventive device.

[0012]A preferred modification of the invention is characterized in that
the course of the belt segments is essentially looped to have
approximately the shape of a T, in which case the individual sheet is
transported--essentially approximately in transverse direction--out of
its original transport direction in order to be later again transported
into its original transport direction. As a result of this, a reliable
turn-over and ultimately the retention of the transport direction are
possible in a reliable manner and, at the same time, the device can be
provided in a highly compact and space-saving manner in a small space.
Overall, another advantage of the inventive device is that available
space can be utilized in three dimensions with more degrees of freedom.

[0013]Another modification of the invention is even characterized in that
the path, along which the individual sheet is carried, provides turning
by a total of approximately 540°, whereby the sheet's upper side
becomes its underside, again its upper side and finally again its
underside.

[0014]Another significant advantage of the inventive device can be seen in
that, in order to form all the belt segments, only one single,
appropriately looped, belt is required, said belt being provided
appropriately looped so that different belt segments of the same belt lie
against each other and, moving in the same direction, become clamping
belt segments for the sheets. In fact, the inventive device can be
implemented, even in a particularly simple manner, with a single belt, in
particular when the transport direction of the sheet is essentially the
same before and after the turn-over process and when the belt segments
are in alignment with each other before and after the turn-over process.
Therefore, in particular, a closed web can also be provided, for example,
with a belt lock. For example, it would also be conceivable to insert a
ready-to-use looped belt with a type of cassette as the turn-over element
into a device, in particular into a printing machine.

[0015]Although, due to the joint deflection of the belt segments and the
individual sheet, the clamping action of the belt segments is enhanced
and secured, it is also possible to provide at least one pair of
deflecting elements, with which the deflecting elements
cooperate--counter-rotating--as counter-bearing elements and form between
them a guide nip for the clamping belt segments. The cooperating
deflecting elements guide the belt segments holding the sheet sort of in
the way of a heated mangle roll, even driving said belt segments, if
desirable.

[0016]Another modification of the invention is characterized in that at
least one first pair of cooperating deflecting elements for moving freely
returning belt segments toward each other is provided to form the
clamping belt segments, and a second pair of cooperating deflecting
elements for the separation of the clamping belt segments is provided to
form the freely returning belt segments. In this manner it is possible to
particularly advantageously guide the freely returning belt segments in a
variable manner and as needed, in particular, when only a single closed
web is used. In such an arrangement, the region of the first pair of
cooperating deflecting elements can be provided for feeding the sheet to
be turned over, and the region of the second pair of cooperating
deflecting elements can be provided for ejecting the turned over sheet,
i.e., sort of form the orifices of the inventive device which, at the
same time offer suitable lateral threading sides for the individual
incoming and outgoing sheets.

[0017]In order to achieve a particularly compact design of the device, it
may additionally be provided that the deflecting elements are arranged
and/or dimensioned in such a manner that the clamping belt segments are
located in the space between the freely returning belt segments, in
particular the freely returning belt segments, so that the returning
belt-segments create a type of enclosure for the device.

[0018]Embodiments of the invention, which could result in additional
inventive features, which, however, do not restrict the scope of the
invention, are shown by schematic drawings.

[0019]They show in

[0020]FIG. 1 a perspective view of the deflecting rollers for a first
embodiment of an inventive turn-over device;

[0021]FIG. 2 a device in accordance with FIG. 1, comprising a transport
belt for the sheets to be turned over, said belt being looped around the
deflecting rollers;

[0022]FIG. 3 a side elevation of the device in accordance with FIG. 2;

[0023]FIG. 4 a perspective view of the deflecting rollers for a second
embodiment of the inventive turn-over device;

[0024]FIG. 5 the device in accordance with FIG. 4, comprising a transport
belt for sheets to be turned over, said belt being looped around the
deflecting rollers; and,

[0025]FIG. 6 a side elevation of the device in accordance with FIG. 5.

[0026]FIG. 1 is a perspective view of the deflecting rollers for a first
embodiment of an inventive turn-over device.

[0027]FIG. 1 is a perspective view showing only the different deflecting
rollers without the sheet-transporting and sheet-flipping web or belt.
The entry for the individual sheet is formed by the deflecting rollers 1b
and 2a, said rollers forming between them a feeding nip for the sheet and
guiding said sheet into the turn-over device in the manner of the rolls
of a mangle, whereby, in so doing, the sheet is transported in a clamped
manner between the belt segments of a belt (not illustrated in FIG. 1 as
already stated), whereby said belt segments are moved toward each other
by the two deflecting rollers 1b and 2a and brought into contact with
each other. In order to be moved toward each other, the free belt
segments of the belt move over deflecting rollers 1a and 2b, to
deflecting rollers 1b and 2a, respectively, into the nip or intermediate
space formed by the deflecting rollers 1b and 2a.

[0028]The belt segments, which have been moved toward each other in this
manner and which carry the sheet to be turned, then move on to a
deflecting roller 7, said roller being oriented at an angle of 45°
relative to the advance direction of the belt segments. The belt segments
transporting the sheet then loop together around the deflecting roller
7--while carrying along the sheet--from the bottom to the top and move
from there to a subsequent deflecting roller 5. During this process, the
sheet is already being turned once by 180°, i.e., its underside is
turned to become its upper side. The advance direction of the belt
segments and the sheet is changed by the deflecting roller 7 by
90° out of the original transport direction.

[0029]The belt segments with the sheets move over the deflecting roller 5
to a deflecting roller 6, and from there to a deflecting roller 8. By
being deflected around the deflecting rollers 5 and 6, the sheet is again
turned by 180°, i.e., its original underside again becomes its
underside.

[0030]Again, the deflecting roller 8 is at an angle of 45° relative
to the advance direction of the belt segments that come from the
deflecting roller 6, and the deflecting roller 8 is at an angle of
90°, i.e., transverse with respect to the deflecting roller 7. The
belt segments also loop around the deflecting roller 8 from the bottom to
the top and then move--taking along the sheet--to the deflecting rollers
3b and 4a. During the deflection of the belt segments around the
deflecting roller 8 the sheet is turned a third time by 180°, and
its original underside again becomes its upper side. Due to the
deflection around the deflecting roller 8, the advance direction of the
belt segments and the sheet again turns into the original transport
direction.

[0031]The deflecting rollers 3b and 4a form an exit gap for the sheet, and
the turned over sheet is ejected from the turn-over device while
maintaining its leading end. When leaving the nip of the deflecting
rollers 3b and 4a, the belt segments separate and move separately and
freely to the deflecting rollers 3a and 4b, respectively, and from there
back to the deflecting rollers 1a and 2b. During this whole process, only
one single belt is used, said belt rotating in a closed manner and being
appropriately looped within itself. While being turned, the sheet is
preferably not accelerated, and the diameters of the deflecting rollers
do not affect the turn-over behavior, but, preferably, the arrangement of
the deflecting rollers relative to each other.

[0032]The movement of the belt as described in FIG. 1 can be repeated
again in FIG. 2, whereby FIG. 2 again shows the deflecting rollers of
FIG. 1, now with a belt, which in this case, too, is a single closed
belt.

[0033]Due to the looping, the belt essentially moves in the form of a T,
namely in the transport direction defined by the entry and exit gaps 1b,
2a and 3b, 4a, and once diagonally downward out of the latter gap to the
deflecting rollers 5, 6 and back again into the transport direction. In
addition, on their paths between the deflecting rollers 1a to 3a and 2b
to 4b, the returning belt segments limit the remaining movement in a
compact manner. Ultimately, this is essentially achieved by the diameters
of the deflecting rollers 7 and 8 and, in view of this, by the distances
of the deflecting rollers 1b, 3b and 2a, 4a from the deflecting rollers
1a, 3a and 2b, 4b.

[0034]FIG. 3 additionally shows the embodiment in accordance with FIG. 2,
in a side elevation. The belt is preferably configured to have such a
width that the sheet is enclosed completely or partially by the belt
surfaces. Preferably, the belt is slightly wider or narrower than the
maximum sheet format desired for transport.

[0035]FIG. 4 shows the deflecting rollers for a second embodiment of an
inventive turn-over device, again initially without belt.

[0036]In this embodiment, the deflecting rollers 12b and 13a form an entry
gap for the sheet to be turned and for the segments moved together which
transport the sheet between them in a clamping manner. From there, the
belt segments then move to another deflecting roller 10 which is oriented
at an angle of 45° relative to the advance direction of the belt
segments. The belt segments loop around this deflecting roller 10 from
the top to the bottom and move to a deflecting roller 11. As a result of
the deflection of the belt segments around the deflecting roller 10, the
sheet is turned over by 180°, i.e., its underside becomes its
upper side. In addition, due to this deflection, the advance direction of
the belt segments is deflected by 90° out of the original
transport direction.

[0037]The belt segments loop around the deflecting roller 11, again from
the bottom, and then move on to a deflecting roller 9. Due to the
deflection around the deflecting roller 11, the sheet is turned over a
second time by 180°, i.e., its original underside again becomes
its underside.

[0038]The deflecting roller 9 is again at an angle of 45° relative
to the advance direction of the belt segments coming from the deflecting
roller 11. The belt segments also loop around this deflecting roller 9,
again from the bottom, and move on to the deflecting rollers 14a and 15a,
which, between them, form an exit gap for the turned over sheets. Due to
the deflection around the deflecting roller 9, the sheet has previously
been turned over a third time by 180°, thereby again making its
original underside its upper side. Furthermore, due to the deflection
around the deflecting roller 9, the advance direction of the belt
segments is again turned by 90° into the original transport
direction.

[0039]When exiting from the exit gap between the deflecting rollers 14a
and 15a, the belt segments are separated and move as free belt segments
from the deflecting roller 14a to the deflecting roller 12a and from
there back to the deflecting roller 12b, or from the deflecting roller
15a to the deflecting roller 15b, from there to the deflecting roller 13b
and from there back to the deflecting roller 13a.

[0040]Therefore, the movement of the belt, which is again just one single
belt, is similar to that of the first embodiment, in particular
essentially T-shaped with respect to the transport direction and enclosed
by the freely returning belt segments. In the two embodiments, the
deflecting rollers 12a, 12b, 13a, 13b correspond to the deflecting
rollers 1a, 1b, 2a, 2b, and the deflecting rollers 14a, 15a, 15b
correspond to the deflecting rollers 3a, 3b, 4a, 4b. The deflecting
rollers 9 and 10 correspond to the deflecting rollers 7 and 8, and the
deflecting roller 11 corresponds to the deflecting rollers 5 and 6. As a
result of the elimination of one deflecting roller 14b, i.e., by
replacing the deflecting rollers 3a and 3b with only one single
deflecting roller 14a, the turned over sheet exits on a level other than
that from where it enters, when viewed in transport direction. By
shifting the deflecting rollers in Z-direction (FIG. 1), however, the
entry and exit in the first embodiment, too, can be located on different
planes.

[0041]Also, the deflecting roller 11, by itself, replaces two deflecting
rollers 5 and 6, and instead has a greater diameter.

[0042]In both embodiments, it is of course possible to reverse the entry
gap and the exit gap, and, in so doing, the transport can take place in
opposite direction.

[0043]FIGS. 5 and 6 show the deflecting rollers of FIG. 4, once again in a
perspective view and in a side elevation with (a single closed) belt.

[0044]One difference in comparison with the first embodiment is that the
sheet in the second embodiment is not always curved in the same direction
when it is being turned over, so that the sheet does not retain a
permanent roll deformation. On the other hand, with both embodiments, a
previously existing roll deformation could be "ironed out".

[0045]Of course, various additional embodiments of the inventive turn-over
device are conceivable. In particular, it is possible, as is basically
shown by the embodiments, that, three times in total, a sheet can be
turned over by 180° by two deflecting rollers each oriented at an
angle of 45° in advance direction and another deflecting roller
oriented in transverse direction. More deflecting rollers could be added
or removed.

[0046]The generated surfaces of the deflecting rollers can be cylindrical
or spherical, whereby spherical deflecting rollers automatically center
the belt. One-piece and split belts--with or without belt lock--are
conceivable. A belt-tensioning device may be provided, and/or the belts
could be elastic. In order to be able to automatically center the belt,
the deflecting rollers could comprise stop collars. In addition to the
belts, additional supplementary guide elements could be provided.